Caulks ordinarily contain colored pigments and mineral fillers dispersed uniformly in a binder to provide a putty-like mastic which can be extruded or trowlled into place. The pliable caulk material is ordinarily applied to a joint to be sealed and hardens at ambient application temperatures to form a resilient continuous barrier between the structural elements to be sealed. The cured or set caulk barrier effectively seals against moisture and air penetration as well as similar liquids and gases. The hardened caulk material desirably exhibits contraction or expansion properties over a long period of time without breaking the continuous sealing barrier. Caulks desirably exhibit useful barrier properties such as elongation, good recovery, low modules, and good adhesion to adjacent substrates.
Acrylic polymers are known to be useful binders for caulk materials and can comprise solvent or water dispersed thermoplastic polyacrylic copolymer. Water dispersed acrylic latex binders are known to provide flexibility, low shrinkage, good adhesion, freeze-thaw stability, and water resistance.
It now has been found that a particularly effective lightweight caulk material can be compounded based on acrylic copolymer latex binders in combination with major amounts of glass microballoon fillers having an average particle size less than about 130 microns or about 90% by weight passing 80 mesh screen size. The resulting low-density caulk material has density of about 4-6 pounds per gallon as compared to conventional caulk materials which typically exhibit 12-13 pounds per gallon. In use, the caulk materials of this invention set to form a high density resilient impermeable barrier exhibiting substantially increased heat and cold insulating properties as well as no appreciably shrinkage. These and other advantages of this invention will become more apparent by referring to the detailed description of the invention.